Orogenic Processes in Seram

Orogenic Processes in Seram, Eastern Indonesia

Jon Pownall, completed PhD project

The Banda region of eastern Indonesia has a complex tectonic configuration which is not yet fully understood. Seram and Ambon, islands of the Banda Arc’s northern limb, have undergone very recent orogenesis and include granites and volcanics as young as 3 Ma. Western Seram is characterised by the association of regional-metamorphic terranes with extensive peridotites, and is traditionally described as a fold-and-thrust belt incorporating northward-obducted ophiolites. However, reconnaissance fieldwork by SEARG and new geophysical evidence suggests recent orogenesis is driven primarily by subduction rollback and resultant lithospheric delamination during a dominantly extensional regime. Shear zones in central Seram are also likely related to such processes.

This project aims, through extensive fieldwork, U-Pb zircon dating, Ar-Ar thermochronology, thermobarometry, and petrological and microstructural analysis, to decipher the recent tectonic evolution of Seram and Ambon. More specifically, it aims to determine the nature of peridotite emplacement, the mechanisms behind granite genesis, the metamorphic history of the ‘basement’ rocks, and explain the presence of higher pressure rocks recently discovered on the island.